test(workflow): erp-workflow 单元测试从 16 增至 63 — 覆盖 model/error/parser/expression/executor

- model.rs: 13 个 FlowGraph 测试（build/outgoing/incoming/start-end 边界）
- error.rs: 7 个 WorkflowError → AppError 转换测试
- parser.rs: 11 个新增验证边界测试（空图/多起点/幽灵边/网关约束）
- expression.rs: 13 个新增求值测试（float/bool/string/复合表达式/空白容错）
- executor.rs: 3 个 is_join_gateway 纯函数测试

crates/erp-workflow/src/engine/parser.rs

@@ -266,4 +266,233 @@ mod tests {
         let result = parse_and_validate(&nodes, &edges);
         assert!(result.is_err());
     }
+
+    // ---- 边界测试扩展 ----
+
+    #[test]
+    fn test_empty_nodes_rejected() {
+        let result = parse_and_validate(&[], &[]);
+        assert!(result.is_err());
+        let msg = result.unwrap_err().to_string();
+        assert!(msg.contains("不能为空"));
+    }
+
+    #[test]
+    fn test_multiple_start_events_rejected() {
+        let nodes = vec![
+            make_start(),
+            NodeDef {
+                id: "start2".to_string(),
+                node_type: NodeType::StartEvent,
+                name: "开始2".to_string(),
+                assignee_id: None,
+                candidate_groups: None,
+                service_type: None,
+                service_config: None,
+                position: None,
+            },
+            make_end(),
+        ];
+        let edges = vec![
+            make_edge("e1", "start", "end"),
+            make_edge("e2", "start2", "end"),
+        ];
+        let result = parse_and_validate(&nodes, &edges);
+        assert!(result.is_err());
+        let msg = result.unwrap_err().to_string();
+        assert!(msg.contains("只能包含一个开始事件"));
+    }
+
+    #[test]
+    fn test_edge_references_nonexistent_source() {
+        let nodes = vec![make_start(), make_end()];
+        let edges = vec![
+            make_edge("e1", "ghost", "end"),
+        ];
+        let result = parse_and_validate(&nodes, &edges);
+        assert!(result.is_err());
+        let msg = result.unwrap_err().to_string();
+        assert!(msg.contains("源节点") && msg.contains("不存在"));
+    }
+
+    #[test]
+    fn test_edge_references_nonexistent_target() {
+        let nodes = vec![make_start(), make_end()];
+        let edges = vec![
+            make_edge("e1", "start", "ghost"),
+        ];
+        let result = parse_and_validate(&nodes, &edges);
+        assert!(result.is_err());
+        let msg = result.unwrap_err().to_string();
+        assert!(msg.contains("目标节点") && msg.contains("不存在"));
+    }
+
+    #[test]
+    fn test_start_event_with_incoming_edge_rejected() {
+        let nodes = vec![make_start(), make_end()];
+        let edges = vec![
+            make_edge("e1", "start", "end"),
+            make_edge("e2", "end", "start"), // start 有入边
+        ];
+        let result = parse_and_validate(&nodes, &edges);
+        assert!(result.is_err());
+        let msg = result.unwrap_err().to_string();
+        assert!(msg.contains("入边"));
+    }
+
+    #[test]
+    fn test_start_event_without_outgoing_edge_rejected() {
+        let nodes = vec![make_start(), make_end()];
+        let edges = vec![]; // start 没有出边
+        let result = parse_and_validate(&nodes, &edges);
+        assert!(result.is_err());
+        let msg = result.unwrap_err().to_string();
+        assert!(msg.contains("出边"));
+    }
+
+    #[test]
+    fn test_exclusive_gateway_single_outgoing_ok() {
+        // 单条出边的排他网关不需要条件
+        let nodes = vec![
+            make_start(),
+            NodeDef {
+                id: "gw".to_string(),
+                node_type: NodeType::ExclusiveGateway,
+                name: "判断".to_string(),
+                assignee_id: None,
+                candidate_groups: None,
+                service_type: None,
+                service_config: None,
+                position: None,
+            },
+            make_end(),
+        ];
+        let edges = vec![
+            make_edge("e1", "start", "gw"),
+            make_edge("e2", "gw", "end"),
+        ];
+        assert!(parse_and_validate(&nodes, &edges).is_ok());
+    }
+
+    #[test]
+    fn test_exclusive_gateway_with_conditions_ok() {
+        let nodes = vec![
+            make_start(),
+            NodeDef {
+                id: "gw".to_string(),
+                node_type: NodeType::ExclusiveGateway,
+                name: "金额判断".to_string(),
+                assignee_id: None,
+                candidate_groups: None,
+                service_type: None,
+                service_config: None,
+                position: None,
+            },
+            make_user_task("task_a", "小额审批"),
+            make_user_task("task_b", "大额审批"),
+            make_end(),
+        ];
+        let edges = vec![
+            make_edge("e1", "start", "gw"),
+            EdgeDef {
+                id: "e2".to_string(),
+                source: "gw".to_string(),
+                target: "task_a".to_string(),
+                condition: Some("amount <= 1000".to_string()),
+                label: None,
+            },
+            EdgeDef {
+                id: "e3".to_string(),
+                source: "gw".to_string(),
+                target: "task_b".to_string(),
+                condition: Some("amount > 1000".to_string()),
+                label: None,
+            },
+            make_edge("e4", "task_a", "end"),
+            make_edge("e5", "task_b", "end"),
+        ];
+        assert!(parse_and_validate(&nodes, &edges).is_ok());
+    }
+
+    #[test]
+    fn test_gateway_without_incoming_rejected() {
+        let nodes = vec![
+            make_start(),
+            NodeDef {
+                id: "gw".to_string(),
+                node_type: NodeType::ParallelGateway,
+                name: "并行".to_string(),
+                assignee_id: None,
+                candidate_groups: None,
+                service_type: None,
+                service_config: None,
+                position: None,
+            },
+            make_end(),
+        ];
+        // gw 没有入边
+        let edges = vec![
+            make_edge("e1", "start", "end"),
+            make_edge("e2", "gw", "end"),
+        ];
+        let result = parse_and_validate(&nodes, &edges);
+        assert!(result.is_err());
+        let msg = result.unwrap_err().to_string();
+        assert!(msg.contains("入边"));
+    }
+
+    #[test]
+    fn test_gateway_without_outgoing_rejected() {
+        let nodes = vec![
+            make_start(),
+            NodeDef {
+                id: "gw".to_string(),
+                node_type: NodeType::ParallelGateway,
+                name: "并行".to_string(),
+                assignee_id: None,
+                candidate_groups: None,
+                service_type: None,
+                service_config: None,
+                position: None,
+            },
+            make_end(),
+        ];
+        // gw 没有出边
+        let edges = vec![
+            make_edge("e1", "start", "gw"),
+            make_edge("e2", "start", "end"),
+        ];
+        let result = parse_and_validate(&nodes, &edges);
+        assert!(result.is_err());
+        let msg = result.unwrap_err().to_string();
+        assert!(msg.contains("出边"));
+    }
+
+    #[test]
+    fn test_parallel_gateway_valid() {
+        let nodes = vec![
+            make_start(),
+            NodeDef {
+                id: "fork".to_string(),
+                node_type: NodeType::ParallelGateway,
+                name: "拆分".to_string(),
+                assignee_id: None,
+                candidate_groups: None,
+                service_type: None,
+                service_config: None,
+                position: None,
+            },
+            make_user_task("a", "任务A"),
+            make_user_task("b", "任务B"),
+            make_end(),
+        ];
+        let edges = vec![
+            make_edge("e1", "start", "fork"),
+            make_edge("e2", "fork", "a"),
+            make_edge("e3", "fork", "b"),
+            make_edge("e4", "a", "end"),
+            make_edge("e5", "b", "end"),
+        ];
+        assert!(parse_and_validate(&nodes, &edges).is_ok());
+    }
 }